English prose literature; Exposition (Rhetoric); Readers -- Science
impressions that characterize different papers. All watermarks,
patterns, and designs which it is desired to have appear in the paper
are put upon this roll and here impressed upon the soft sheet, which is
clarified and left transparent at the point of contact. Thus the
impression is permanently fixed in the fiber, so that it can be seen at
any time by holding the sheet to the light. The power of suggestiveness
is a quality which is highly esteemed wherever it is found, and which
frequently furnishes a standard of judgment.
Judged by such a criterion, the impression cylinder, or "dandy roll,"
has an added value, for in all probability its operation suggested the
idea of printing from cylinders, as in our present web or perfecting
presses.
The matted pulp, now having sufficient body, passes on between two rolls
covered with felt which deliver the web of damp paper upon an endless
belt of moist felt, while the "wire" passes under and back to continue
a fresh supply. The paper is as yet too fragile to travel alone, and
the web felt carries it between two metal rolls called the first
press-rolls. These squeeze out more water, give a greater degree of
compactness to the fibers, smooth the upper surface, and finally deliver
the web of paper to a second felt apron which carries it under and to
the back of the second press-rolls. In this way the under surface comes
to the top, and is in its turn subjected to the smoothing process. A
delicate scraper or blade, the length of the press-rolls, is so placed
on each roll that should the endless web from any cause be broken, the
blade may operate with sufficient force to prevent the wet paper from
clinging to the rolls and winding about them. From this point the paper
travels alone, having become firm and strong enough to sustain its own
weight; passing above the second press-rolls, it resumes its onward
journey around the drying cylinders, passing over and under and over and
under. The drying cylinders are hollow and heated by steam, their
temperature being regulated according to requirements. These driers,
made from iron or steel, are usually from three to four feet in diameter
and vary in length according to the width of the machine. There are from
twelve to fifty of these cylinders, their number depending upon the
character and weight of the paper to be produced, very heavy sheets
requiring many more drying cylinders than sheets of lighter weight.
Public-domain text, read in full here on John Shaqi.
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